Cos 140+cos 100+ cos 20
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Adintipan22
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Cos 140+cos 100+ cos 20
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1. Jawaban Anonyme
jawab
(cos 140 + cos 100) + cos 20 =
= 2 cos 1/2 (140+100) cos 1/2 (140 -100) + cos 20
= 2 cos 1/2 (240) cos 1/2 (40) + cos 20
= 2 cos 120 cos 20 + cos 20
= 2 (- 1/2) .cos 20 + cos 20
= - cos 20 + cos 20
= 0